Process of vulcanizing rubber and products obtained thereby



Patented Mar. 4, 1941 PROCESS OF VULGANIZING RUBBER AND PRODUCTSOBTAINED THEREBY Robert L. Sibley, Nitro, W. Va., assignor to MonsantoChemical Company, St. Louis, Mo., a corporation of Delaware No Drawing.Original application October 23, 1930, Serial No. 490,814. Divided andthis application June 18, 1938, Serial No. 214,575

4 Claims. (Cl. 260-789) Thi invention relates to the vulcanization ofpressures and for variou periods of time, The rubber by an improvedprocess, wherein there cured stock was thentested to determine its isemployed a member of apreferred class of modulus and tensile strengthunder various decompounds which improve the action of the acgrees ofelongation. The results of the tests of 5 celerator used in thevulcanization process and the rubber composition thus described are set5 with them form a mixed accelerator. The preforth in the followintables. Table I gives the ferred class of compounds employed in the man-7. results when diphenylguani-dine hydrochloride is ner hereinafterdescribed comprises salts of a employed as an example of the preferredclass guanidine and derivatives thereof. of compounds and Table II givesthe results As examples showing the use of the preferred whendiphenylguanidine benzoate is so used. 10

Table I Number Modulus of elasticity in dpfirtsl lbs/111.; at elonga-53017 111; Ultimate 15 1p eny 1011s 0 S. 111. 6 onga- Tune of curegnanidine at tion,

hydrobreak percent chloride 300% 500% 700% None 85 133 340 1140 990 15min. at 10 lbs. steam per sq. in 0. l 84 151 422 1845 980 20 7 0. 2 94185 440 1970 980 None 108 201 556 1870 030 20 min. at 10 lbs. steam persq. in 0.1 97 200 675 2095 910 0. 2 130 241 740 2185 910 None 131 300952 2405 875 30 min. at 10 lbs. steam per sq. in 0. 1 105 312 1070 2640875 0. 2 157 328 1000 2810 880 20 None 315 963 3400 4260 750 1% hrs. at20 lbs. steam per sq. in 0.1 356 1040 3620 4320 750 335 1005 3850 4380745 Table II M 5111 r 1 t' '1; in 30 4 o usoeasiciy N85,?! lbs/in. atelonga- Tensile Ultimate Time of cure diphenylmom i guanidine b abemoate reek percent None 85 133 349 1140 090 15 min. at 10 lbs. steamper sq. in 0. 1 93 173 440 1720 980 i 0. 2 88 173 433 1803 970 1, None108 201 I 556 1870 930 20 min. at 10 lbs. steam per sq. in 0 1 133 227709 2040 910 0 2 132 236 661 2210 030 None 131 300 I 052 2465 875 40 30min. at 10 lbs. steam per sq. in '0. 1 140 311 1183 2650 865 0 2 152 3221045 2665 875 None 315 903 3400 4260 750 1% hrs. at 20 lbs. steam persq. in 0. 1 316 1000 3580 4250 745 0. 2 320 1055 3710 4200 735 45 classof compounds, a rubber mix was prepared It is readily apparent from thedata set forth in in the well known manner comprising 100 parts Tables Iand II that the preferred class of maof pale crepe rubber, 5 parts ofzinc oxide, 3 terials possess highly desirable activation propparts ofsulfur, 0.5 part of the crotonaldehyde erties; Q derivative of thereaction product of mercapto- As examples of the use of the preferredclass 50 benzothiazole and hexamethylenetetramine, 0.5 of compounds,showing retarding effect in the part of diphenylguanidine, and. 0.1and/or 0.2 shorter timed and'lower steam pressure cures part of acompound of the preferred class of and activation in the longer timedand higher activators as hereinafter mentioned. The mix steamhpressurecures, the following three rubwas then vulcanized by heating undervarious ber stocks, designated A, B and C were 55 prepared and tested inthe manner hereinbefore set forth.

curing process in the longer timed and higher steam pressure cures, butalso greatly retard the cure in the shorter timed and lower steam pres-Stock sure cures. This retardation of cure at the lower Stock A stock BC temperatures is a highly des rable property, as scorching orvulcanizing on the mixing rolls is Pale crepe rub'bst 35 5% 0,55 therebysubstantially prevented. Zinc Oxide 8 8 8 As further examples of the useof the preferred Sulfur 1. 2.5 2.5 2.5 steam acid 0,5 0.5 M class ofmaterials, a rubber mix was prepared f gg g igggg a igg g gl gffi gcomprising 100 .parts of pale crepe rubber, 5 parts 10gexamethylenetetrgminei"if"? 3 0.4 0.4 0.4 of zinc oxide, 3 parts ofSulfur, 1 p of stearric glggggfigggg ggg acid, 0.4 part of theacetaldehyde derivative of Diphenylguanidine acetam III: (1'0the-reaction product of para-para-diamino-diphenyl-methane andmercaptobenzothiazole, and

- r' The results of the tests upon the above described 1- 8 i hPreferred Class Of marterlals- The rubber stocks after curing forvarious periods of results of 8111 11 the ve -l er stock time and undervarious steam pressures are after curing are Elven 1n the fOllOWlhg t egiven in Table III, which shows by comparis Table IV gives the resultsof tests of the cured the desirable effect of the presence of acomrubber Product 111 which p y ua pound of the preferred class, as forexample di- D t e Was incorporated in the fe 20 phenylguanidinephthalateand diphenylguaniscribed rubber stock prior to the vulcamzation dineacetate, on the cure of a rubber stock of thereof. Table V gives theresults of tests obvulcanization characteristics. tained whendiphenylguanidine hydrochloride Tab e III Modulus of elasticity Steam 7in lbs/in. at elonga- Tensile Ultimate Cure mins Pressure Stock 103.011at break tion' lbs/in. percent 11 54 98 188 1195 1090 15 10 B V V l B Eo 05 103 224 1085 1040 A 117 228 818 2300 895 30 :10 1B 0 100 189 0212135 030 A 194 440 .1775 3235 810 00 10 B 131 225 708 2235 900 o 185 4341730 3505 835 A 28 182 592 2120 935 10 20 1B c 87 135 387 1413 950 A 182382 1450 3040 830 20 20 B 90 139 334 1000 920 0 168 307 1158 2825 860 A189 475 1870 3395 800 30 20 B 132 254 910 2445 870 0 170 454 1850 3405815 A 230 038 2575 3895 705 '45 20 B 184 418 1710 2820 790 c 259, 6582725 3770 700 .4 300 085 2920 3940 780 00 20 B 221 587 2300 3020 790 0308 40 3170 4070 745 .4 315 00s 3020 4175 710 90 20 B 285 810 3200 4200755 1 o 318 1095 4320 4420 710 A 293 900 3595 4410 730 120 20 B 282 7503080 3925 750 0 309 990 3900 4415 725 1 Cure insufiicient for test. 2 Notest made. 7 A comparison of the results given in Table III was employedin the manner described above, and shows that the preferred class ofmaterials as Table VI sets forth theresults obtained when difor examplediphenylguanidine phthalate and diphenylguanidine acetate was employedin the phenylguanidine acetate, not only activate the above identifiedstocks in the manner described.

Table IV Modulus of elasticity in lbs./in. at elonga- Tensile UltimatTime oicure nous lbs/in. figg I atbreak perceat 300% 500% 700% 20 min.at 10 lbs. steam per sq. in "89 2080 970 25 min. at 10 lbs. steam persq. in.-- 131 2285 890 30 min. at 10 lbs. steam per sq. in.-. 141 2835860 "[0 15 min. at 20 lbs. steam per sq. in 159 3260 '885 30 min. at 20lbs. steam per sq. in..-" 253 4310 s00 45 min. at 20 lbs. steam per sq.in. 323 4685 760 1 hr. at 20 lbs. steam per sq. 1.11.. 418 4610 700 1%hrs. at 20 lbs. steam per sq. 418 4610 700 2 hrs. at 20 lbs. steam persq. in. 441' 4455 675 at break of 2780 lbs/ins. and an ultimateelong'ation' f 920%. The foregoing tests given in Tables IV, V and VIshow that the preferred class 01i. activating materials, when employedin the rubber stock described, retards or delays the curing-gactionduring. the early stages or the vul- -'caniza.tion process but permitsthe accelerator to exert substantially its normal effect at full cure.in fact, the.:mater1als appear to. first serve as retarders-and later asactivatorsat least, the

'full activating effect of the materials is not produced during theearly stages of the cure.

. As afurther example of the.use of the preferred.v class of-materials,. a. rubber stock was 'sgesaeeo Table V Modulus. olelasticity I mills/in. at eionga- Tensile Ultimate Time of cure nouslbsJin. gg? 5 at break percent 3 7 20 min. at lbs. steam pel. sq. in 128255 335 2050 925 25 min. at 10 lbs. steam per sq. in--. 148 322 12052905 875' 30 min. at 10 lbs. steam per sq. 163- 378 1450 3675 875- 1.0mm. at lbs. steam per sq. in 156 400 1570 3190 860 30 min at 20 lbs.steam per sq in..- 255 741 2830 4200 795 45 min at 20 lbs. steam per sqin.-- 326 1115 3945 4510 745 1 hr. at 20 lbs. steam per sq. in 411 15254728 4775 705 1% hrs. at 201bs. Steam per Sq. in 411 1525 4728 4775 7052 hrs. at 20 lbs. steam per sq. in 459 1718 4945 685 A 1 5 Table VIModublul} o t elasticity UW t m s. m. a e ongef Tensile lmae; Time ofcure tions lbs/in. 11 85 l at break percent 300% 500% 700% 20 min. at 10lbs. steam per sq. in 76 133 346 1375 985 min. at 10 lbs. steam per sq.in 92 180 512 2080 975 min. at 10 lbs. steam per sq. in 104 226 721 2328955 25 15 min. at 20 lbs. steam per sq in 110 228 754 2375 955 30 min.at 20 lbs. steam per sq in 174 896 1472 3315 870 45 min; at 20 lbs.steam per sq m 215 560 2015 .3780 830 1 hr. at 20 lbs. steam per sq. m261 732 2655 3850 775 1% hrs. at 20 lbs. steam per sq. in. 261 732 26553850 775 2 hrs. at 20 lbs. steam per sq. in 279 776 2780 3990 770 l 30 Astock identical with that employed in the test given in Tables IV, V andVI with the excep n h dip nylsuanidine was substituted The results ofthe tests upon the above rubber for the diph nyl l s, on curing for 20stock after curing are given in Table minutes at 10 lbs. steam pressuregave a tensile Table VII v Modulus of elasticity in lbsJin. at elonga-Tensile Ultimate Time of cure lbs mt ag? Y at 759*? percent 50 20 min.at lo lbs. steam per sq. in) 30 min. at 10 lbs steam per sq 200 890 23502955 790 10 min. at 20 lbs steam per sq in 200 578 1550 2285 825 15 min.at 20 lbs steam per 5 301 925 2470 2865 750 l 30 min. .at 20 lbs. steampers 301 1140 2960 3500 760'- 45 min. at 201m. steam per sq. in.. .4041250 3185 350,5.- 735 60 min. at 2010s. steam persq. in 434 1280 036.03515 720 1 Did not cure.

It is readily apparent from, the-results set forth in Table VII that inthe presence of one of the preferred class of materials, for example,diphenylguanidine phthalate, the vulcanization is retardedin the earlyperiod of the cures, but ,this retarding effect is .not continued in the5 --longer cures and the cures at the higher steam .pressures- 1- Asafurther example of the use of the preferred class ofwmaterials, a rubberstock was pre- Table VIII elasticity UH t p I. Jaeonga- T n 111186 8Time ofcu're Hons lb ffinfl ggg I v v, at break percel'lt 20 min. at 10lbs. steam per sq. in. u 10 30 min. at 10 lbs. steam per sq.'in. 177 4961315 1850 10 10 min. at 20 lbs. steam per sqnnl min. at lbs. steam persq. in 21-5 665 1850 2450 3'9 min. at 20 lbs. steam per sq. in a 306 9602600 3360 min. at 20 lbs. steam per sq. in" 374 1155 3050 3420 I min. at2 0'lbs. steam per sq.fin '412 1265 3185 3340 1 Did nji cure. 15

i Not fit for test.

It is apparent from the results set forth in The results of the testsupon the above rubber 20 Table VIII that in this examplealso, as inprestocks after curing aregiven in Table IX. :20

Table IX Modulus efelastie-v t 6 I 6 Steam ity in lbs/in. at TensileUltimate Cumming pressure Stock elongations of lbs lint elqnga:

' 'atbre'a k lbs/111., percent 300% .'50

A 2110a 1.66sv 590 B sec 030 520 1 a Y; .1568! 2370a 1,,B 21290- 21850620' "A '3440- -630 -A 2270 3395 635 "B 1070 2680 600 A 2890 4490 070 B2480 3610 625 A 3445 4030 625 B 3020 4320 020 A sass 4860 610 40 B 36054005 610 A 4100 4860 570 a 3725 4125 590 "*5 I v j l, Q :1 illousexamplescitedthe presence of one of the a Acomparison' of the resultsgiven in Table IX "preferred classof materials, for example, dijgivesfurtherproof 't-hatthe presence of one of'phenylgu'anidine"phthalate, retards the 'vulcan- {the preferredc'lassofmaterials, for example, di- L ation process in the shorter timedcures, but the {phenylguanidine acetate, retards thevulcanizaulc'aini'za'tion of the compounded rubber stock -tion in theshorteritimedrande lower steame'presj hr'eim 'the preferred 'cl'as'sofmaterials "is in- 1 sure'euresmutsactivates the'vulcanizationjni the f'rporated-isnot-retarded on the-longer heating longer":timed andhigherzisteam: pressurezcures. riod'an'd at the higher steampressure-cures. The results. hereinbefor set, forth ::show., -that V-'As'fiirther exampleslof the use'ofthe preferred avulca'n'ized rubberproduct -ofrparticularly high 1' ;c 1 as -or maperi 1s, tworubberstocks, designated quality is obtained by :employing .a"the..prefem ed ,5 *A'f-"and --B, were prepared'and tested for comsnbstancesin: a rubber'stock, of'vulcanizing charparison, stock Af comprisingdiphenylguanidine aoteristics. p as fan activator' and stock Bcomprising di- Other-salts ofguanidines than thosehereinbeph'enylguamdine acetate in its stead as one-of :"fore set forthmay :be'employed-fins.themanner the preferred class of materials. Therubber described. 'IFhus,the.phthalate?'hydrochloride, -.B0 v stookshere referred to comprised the following acetate,-xand similarisaltsvbfdiedztho-tolyb-uanin redients: idine;ylylguanidines;triphenylguanidlnesaand .6 wanalogousecorhpoundsnmaysbeemployedi in'it-he H f vulcanizationl ofgmbberrimqai mann'er ;analogous'65 Smck B tolthat hereinbefore set forth.

Pam p" 'l' his inyention is not're'stricted to thellsetjof smo edsheembberw "100 $30 e t ula compounds given in theidisclosure g g fe e e39 J 9 as examples, nor is'it'"restrictd to 'the useipf the 'ifif f t 5preferred class of compoundsiri'thejparticiflar '70 gsird:ggnineralandvegetable m1 2 rubber mixes herein" described. "The inventiongisxqetsmeh d'div tiBHiJEEcfiH-fbi limited y by'theblailfisatta'fihedher'fiimaswpart .9 23 of -g g i fi fi f b 6 of the presentsp'edifi'catiorl. I I sttetittt n tti .fi.if:::::: '67s; T nli is adivision f n nd ns p v e se acetate, application Serial" No; T49U,814,fffi1ed oet heriza,

2,2eaeeo What is claimed is:

1. The process of vulcanizing rubber which comprises heating' a mixtureof rubber and sulfur in the presence of a mercapto-aryl-thiazolea'ccelerator and in addition thereto a diary] substituted guanidine saltof hydrochloric acid.

2. The process of vulcanizing rubber which comprises heating a mixtureof rubber and sulfur in the presence of a mercapto-benzo-thiazoleaccelerator and in addition thereto diphenyl guanidine hydrochloride.

3. The vulcanized rubber product produced by heating rubber and sulfurin the presence of a mercapto-aryl-thiazole accelerator and in additionthereto a diaryl substituted guanidine salt of hydrochloric acid.

4. The vulcanized rubber product produced by heating rubber and sulfurin the presence of a mercapto-benzo-thiazole accelerator and in additionthereto diphenyl guanidine hydrochloride.

ROBERT L. SIBLEY.

